Ultrasonic imaging has found several applications in the medical field, especially to view internal anatomical tissue and structures. One well known application, for example, is to use a hand held ultrasonic probe to image a developing fetus during pregnancy. Ultrasonic imaging has also found application in laparoscopic surgery, such as in the performance of biopsies and excision of internal organs or other tissue.
Laparoscopic surgery involves the use of small diameter tools that are inserted into a patient's body cavity through a small hole in the abdominal wall. The hole is made by puncturing the abdominal wall with a sharp edged instrument called a trocar. A small working tube, called a cannula, is then inserted into the hole to hold it open. Through the internal passageway of the cannula, often referred to as a surgical port, are passed the necessary instruments into the body cavity to perform desired surgical operations.
Normally, the trocar and cannula are configured in a single structure. Also, the cannula is usually fitted inside with some type of sealing apparatus, such as, for example, a flapper valve that can be forced open by a tool entering through the cannula, and which springs closed to seal the internal passageway through the cannula when not in use. The cannula can also be fitted with annular sealing devices for sealing between a probe inserted through the cannula and the inside wall of the cannula. Such a means for sealing the passageway of the cannula prevents contaminants from the outside environment from invading the body cavity, thereby reducing the possibility of infection.
Various probes have been used to aid laparoscopic surgical operations. For example, optical probes are often used to view the outer surfaces of internal organs. Also, ultrasonic probes have been used to assist in viewing the internal structures of organs to obtain information that may be necessary for performance of certain surgical operations. For example, a surgeon might need to be able to identify and distinguish the cystic duct from the common duct in the gall bladder/liver to perform certain procedures.
A variety of ultrasonic probes have been used in laparoscopic procedures. One type of probe has a single transducer that is mechanically moved through an arc to transmit or receive ultrasonic signals over a pie-shaped area. Such a mechanical sector scanner can be positioned on a probe to image in either a forward or a side direction. A second type of ultrasonic probe that is used to transmit or receive ultrasonic signals over an area contains several transducer elements arranged in an array. One type of array probe that has been used contains several transducers arranged in a line along the side of a cylindrically shaped probe. Such a linear array provides side imaging capability. Another type of array probe aligns the array of transducer elements along a curve at or near the end of a probe to provide forward looking capability. Such a curved array transmits and receives ultrasonic signals over a pie-shaped area like the mechanical sector scanner. Although working well for forward viewing that is useful as a general directional and positional guide, curved arrays are not well suited for imaging near the probe, as is often desirable during surgery, because of a limited field of imaging in the region near the curved array.
During laparoscopic surgical operations, ultrasonic imaging in a forward direction beyond the end of the probe is often required. Ultrasonic imaging to the side of the probe, however, is also often required. The ability to do both forward and side imaging are desirable during some operations. For example, forward imaging can be used to determine when a probe is at the location into the body cavity for side imaging organs or other tissue of interest which cannot be adequately viewed with a forward imaging probe.
Typically, when a need exists for both forward and side imaging, two separate probes are used, one for forward imaging and one for side imaging. For example, a forward imaging probe might first be inserted so that a surgeon can determine the proper distance into the body cavity at which the operation is generally to be performed and possibly also to locate an organ or other tissue of interest. The forward imaging probe is then removed and a side imaging probe is inserted to obtain a better view of the organ or other tissue of interest in preparation for a medical operation that is to be performed on the tissue, such as excising tissue or taking a biopsy sample. The use of two probes, however, is awkward. It is difficult for a surgeon performing a complex operation to mentally reorient between the forward and side looking images. Also, assuring proper repositioning of the probe at the proper distance into the body cavity can present a problem.
One attempt to provide some degree of both forward and side looking capability in a single probe has been to place a linear array at some acute angle relative to the longitudinal axis of the probe. Such an angled array, however, provides limited imaging capability in either the forward or the side directions, and is, therefore, of limited practical utility.
Another attempt to provide some degree of both forward and side looking capability in a signal probe has used a mechanically scanned ultrasonic transducer. These probes, like the probes using the angled array, have proved to be of limited practical utility due to their limited imaging capability in the forward and side directions. Moreover, the moving parts associated with mechanical scanners render the probes more susceptible to malfunction.
Based on the foregoing, there is a need for an ultrasonic probe that addresses the noted deficiencies of presently known probes in providing both forward and side imaging capability.
Presently, ultrasonic images produced by ultrasonic medical probes are displayed on a video monitor with a fixed frame of reference. The image is typically displayed on the monitor from top to bottom, with the distance away from the ultrasonic probe increasing going down the screen. Therefore, tissue nearest the ultrasonic probe is displayed at the top of the monitor and tissue farthest from the probe appears at the bottom of the monitor.
A surgeon, or other medical professional, viewing the ultrasound image must mentally translate the image as displayed on the monitor to a frame of reference in the patient's body, thereby orienting the image in order to properly locate organs or other tissue of interest. Also, when the probe is moved from one position to another, or rotated to image in a different plane, the surgeon must also mentally reorient that new image relative to the old image. For example, if the surgeon is viewing a first ultrasonic image with the probe in a first position looking sideways and then rotates the probe counterclockwise to produce a second image, the surgeon must mentally translate the second image counterclockwise from the first image to properly conceptualize the patient's anatomy. These mental translations and orientations of images can be difficult to make as well as potentially distracting during complex surgical operations.
Consequently, there exists a need to provide the surgeon with an ultrasonic image that reduces the mental image translations that the surgeon must presently make each time the probe is moved to obtain a new image.
Many laparoscopic surgical operations require cutting, or excision, of internal tissue. The tissue to be cut as well as other internal structures must be located and properly identified prior to performing the cutting operation. For example, it may be necessary to locate and identify the common duct that runs through the liver so that a subsequent cutting operation on the liver will not nick or sever the duct.
Presently known methods for performing cutting operations during laparoscopic surgery use techniques for locating and identifying tissue that present significant potential for cutting the wrong tissue. For instance, one method for locating, identifying, and cutting tissue involves inserting an ultrasonic probe into the patient's body cavity to locate and identify the tissue to be cut and internal structures to be avoided. The ultrasonic probe is then removed and a surgical instrument is inserted and positioned to perform the cutting based on the information obtained from the ultrasonic probe. Positioning the surgical tool to properly perform the desired cut, however, based upon the information provided by the ultrasonic probe may be difficult, and it is possible that an improper cut can be made.
Therefore, a need exists for reducing the possibility that an improper cut or excision is made.
One problem often encountered with performing ultrasonic scans during laparoscopic operations is establishing good ultrasonic contact between ultrasonic transducers and tissue, the underlying structure of which is to be imaged. Good ultrasonic images can be produced only if adequate ultrasonic contract, often referred to as coupling, can be made between the tissue and ultrasonic transducers. Obtaining such ultrasonic contact is often difficult. For example, an ultrasonic device may be on the side of a probe, but only the tip of the probe can be contacted with the tissue of interest. Or, for example, it may be possible to contact the ultrasonic device and the tissue of interest, but in so doing the tissue is physically distorted and, therefore, the ultrasound image produced may be misleading.
One approach that has been used to establish ultrasonic contact with tissue is to fill the body cavity space in which the tissue resides with an ultrasonically transmissive fluid, such as water. However, this technique results in large amounts of transmissive fluid invading the body cavity. Transmissive fluids placed in the body cavity must normally be removed following the ultrasonic imaging operation. Assuring that large amounts of transmissive fluid have been completely removed from the body cavity can be troublesome.
Another problem with laparoscopic probes is that they are difficult to sterilize. One attempt to resolve the sterilization problem has been to place a sterile disposable cover, or sheath, over the laparoscopic probe prior to insertion of the probe into a body cavity. After removal of the probe, the sheath is discarded. As a consequence, the need for extensive sterilization of the probe is reduced.
One type of sheath that has been used to cover laparoscopic probes is a loose fitting, thin-walled, highly flexible prophylactic sheath made of an elastomeric-type material, such as latex rubber. One problem with the loose fitting prophylactic sheath however, is that it tends to catch and bind in the seals and/or a flapper valve in the cannula thereby inhibiting insertion and extraction of the probe. In extreme cases, the prophylactic sheath may tear, thereby defeating the very purpose of the sheath in providing a sterilized surface.
Another type of sheath that has been used is a thin-walled, tightly fitting, highly flexible sheath made of elastomeric-type material, such as latex rubber. The sheath is fitted on the probe by first inflating the sheath, like a balloon, and then inserting the probe into the inflated sheath. The sheath is then deflated to tightly fit around the probe. Because of the thin-walled, highly flexible nature of the sheath, however, there is still potential for binding in the cannula. Also, the procedure of fitting the sheath onto a probe is time consuming and awkward in the surgical environment. One related problem with using the sheaths just discussed, is assuring that an ultrasonically transmissive circuit is established between the ultrasonic device and the sheath. Currently, ultrasonic coupling between the ultrasonic device and the sheath is established by coating the probe with an ultrasonically transmissive fluid before covering the probe with a sheath. This procedure, however, is inconvenient, time consuming and awkward in the environment of an operating room.
Based on the foregoing, there is a need for establishing an ultrasonic device that can ultrasonically couple the transducer to the tissue of interest that avoids or reduces the problems associated with using large amounts of ultrasonically transmissive material to establish the requisite coupling.